Pulse or digital communications – Bandwidth reduction or expansion – Television or motion video signal
Reexamination Certificate
1998-05-15
2001-04-03
Britton, Howard (Department: 2613)
Pulse or digital communications
Bandwidth reduction or expansion
Television or motion video signal
C348S384100, C382S243000
Reexamination Certificate
active
06212234
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a technology for encoding/decoding an image, in particular, a color image.
2. Description of the Prior Art
Recently, color documents are rapidly widespread, and a data amount of documents is increasing several times the data amount of the past. Therefore, in order to reduce document input and output times, there is requested a color image compression coding system for compressing color image data at a high speed with a high compression ratio.
There are available a color image expression system in which image data is separated per color element such as K (black), Y (yellow), M (magenta), C (cyan) and expressed (this system will hereinafter be referred to as a field-sequential system) and a color image expression system in which image data is not separated per color element and expressed (this system will hereinafter be referred to as a dot-sequential system). These examples will be described with reference to memory areas
701
and
700
of FIG.
15
. In the example of the field-sequential system expressed by the memory area
700
, R (red) signal data, G (green) signal data and B (blue) signal data are memorized separately. In the example of the dot-sequential system expressed by the memory area
701
, an R pixel value, a set of a G pixel value and a B pixel value expressing pixels are memorized at memory locations corresponding to the pixel positions of image. Data expressed by the dot-sequential system is read out as it is and processed when it is displayed on a CRT (cathode-ray tube) in a dot-sequential system. According to the dot-sequential system, an image can be drawn at a high speed and the dot-sequential system is widely used on a computer. On the other hand, an electrostatic photography color printer executes an electrostatic photography process at every element. Accordingly, the field-sequential system is widely used in this kind of color printer. For this reason, it is frequently observed that an image of a dot-sequential system handled by the computer is outputted by a field-sequential system printer.
A conventional example in which a dot-sequential system image is outputted by a field-sequential system printer will be described below. In the following description, a color image comprises four colors of K, Y, M, and C.
CONVENTIONAL EXAMPLE 1
FIG. 16
shows the manner in which a color image is outputted to a color printer by use of an image encoder and a decoder both of a conventional type. In this example, inputted dot-sequential color image is converted into a field-sequential system color image, and each field is encoded/decoded as a gray-scale image, and outputted to the printer of field-sequential system. The dot-sequential/field-sequential conversion is executed by a central processing unit (CPU).
In
FIG. 16
, reference numeral
100
denotes an encoder for encoding image data,
101
a decoder for decoding encoded image data,
103
a storage/playback work memory,
104
a hard disk (HDD) for temporarily storing encoded image,
105
a color printer for inputting and outputting an image in the field-sequential system, and
108
a CPU for controlling this system. Reference numeral
200
denotes a system bus for connecting each module in this system.
In
FIG. 16
, when an image is outputted to the printer, the work is separated into two processes of first-stage processing and second-stage processing. The first-stage processing covers the processing executed until an image is stored in the HDD
104
, and has the following procedure. Let it be assumed that an image outputted to the color printer
105
is already stored in the memory
103
. The CPU
108
converts a dot-sequential system image into a field-sequential system image.
FIG. 17
shows the contents of the conversion work. Let us consider the case in which a dot-sequential system image is stored in a memory area
810
on the memory with each of K, Y, M, C fields being of 8 bits and 32 bits in total, converted into K, Y, M, C fields, and stored in memory areas
816
,
817
,
818
,
819
on the memory, respectively. The CPU
108
reads out a value
811
of one pixel of 32-bit width from the memory area
810
, decomposes the same into four of element data
812
,
813
,
814
,
815
by 8 bits each from the high-order bit sequentially, and regard them as pixels of K, Y, M, C fields. Finally, the CPU
108
writes the element data
812
,
813
,
814
,
815
of 8-bit width in corresponding memory areas
816
,
817
,
818
,
819
. When this work is effected on all pixels by scanning the address positions of the memory areas
810
,
816
,
817
,
818
,
819
as shown by arrows
820
,
821
, the image is converted from the dot-sequential system into the field-sequential system. Since the image of field-sequential system is generated, the CPU
108
informs the fact that the image data is prepared in the memory
103
through the bus
200
to the encoder
100
. The encoder
100
reads out image data from all of the four fields of K, Y, M, C, encodes the same and writes encoded image encoding data through the bus
200
in the memory
103
, and informs the completion of the encoding through the bus
200
to the CPU
108
. The CPU
108
informs the fact that image data of all fields of Y, M, C, K are all prepared in the memory
103
to the HDD
104
through the bus
200
. The HDD reads out image encoding data of all fields of Y, M, C, K through the bus
200
and stores the same inside. The above-mentioned processing is repeated until output image data is gone. Normally, the repeated processing is executed by the unit of one page.
The second-stage processing is executed until image data is outputted from the HDD
104
to the color printer
105
, and its procedure is as follows. The CPU
108
issues a command through the bus
200
to the HDD
104
in such a manner that HDD
104
reads out image encoding data of all fields of the Y, M, C, and K. The HDD
104
reads out the image encoding data, outputs the image encoding data through the bus
200
to the memory
103
and informs the fact that the reading of the image encoding data is finished through the bus
200
to the CPU
108
. The CPU
108
outputs the fact that the image encoding data is prepared in the memory
103
through the bus
200
to the decoder
101
. The decoder
101
reads out the image encoding data through the bus
200
, decodes the same, writes the decoded image data through the bus
200
in the memory
103
, and informs the fact that the decoding is finished through the bus
200
to the CPU
200
. Then, the CPU
108
informs the fact that the image data is prepared in the memory
103
through the bus
200
to the color printer
105
. The color printer
105
outputs the out image data thus read through the bus
200
. Similarly to the first-stage processing, the above-mentioned processing is repeated until outputted data is gone.
An image encoding system of the encoder
100
may be an encoding system which can encode and decode image data of field-sequential system. Herein, a drawing direction predictive encoding system (Japanese Patent Application No. Hei 8-31074) that has been proposed by the assignee of the present application. As shown in
FIG. 2
, according to this drawing direction predictive encoding system, when a pixel is encoded by scanning image data
301
as shown by an arrow
303
, the encoding is carried out by predicting the drawing direction. As shown in
FIG. 3
, for example, a pixel
305
around an encoded pixel (target pixel)
304
is referred to. If the target pixel
304
and the reference pixel
305
are arranged in a pixel value group
306
shown in
FIG. 4
, a same pixel distribution
307
is generated. In this same pixel value distribution, 0 indicates disagreement, and 1 indicates agreement. On the basis of this same pixel distribution, there is labeled a reference pixel value (A, B, C, D) shown in
FIG. 5
, for example, and codes shown on a table
309
are generated. The codes thus generated are called predictive information codes. If none of the tar
Andoh Akihiro
Yokose Taro
Britton Howard
Diep Nhon T
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
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